Methods for use in dental articulation

ABSTRACT

A computer implemented method includes providing a first set of digital data corresponding to an upper arch image of at least a portion of an upper dental arch of a patient, providing a second set of digital data corresponding to a lower arch image of at least a portion of a lower dental arch of the patient, providing bite alignment data representative of the spatial relationship between the upper dental arch and the lower dental arch of the patient, and aligning the upper and lower arch images relative to one another based on the bite alignment data until an aligned upper and lower arch image is attained. The aligned upper and lower arch images are moved towards each other until a first contact point is detected and at least one of the upper and lower arch images is moved relative to the other in one or more directions to a plurality of positions for determining optimal occlusion position of the lower and upper dental arches.

FIELD OF THE INVENTION

[0001] The present invention relates to dental articulation. Moreparticularly, the present invention pertains to methods for use indental articulation which use digital data that corresponds to images ofa patient's upper and lower dental arches.

DESCRIPTION OF THE RELATED ART

[0002] Dentists, orthodontists, prosthodontists and others engaged invarious fields of dentistry often have use for a model or replica ofselected areas of a patient's oral cavity. For example, a dentist orprosthodontist may desire to have a model of an area of a patient's oralcavity where one or more teeth are missing or damaged, so that suitablereplacement teeth may be made in the lab using the model as a guide. Inpractice, the replacement teeth may be fitted by trial and error on themodel and adjusted in size and shape as needed until a satisfactory sizeand shape are attained.

[0003] As another example, orthodontists often use models of a patient'steeth to study malformations of the teeth and jaws and plan a course oftreatment. In some instances, the orthodontist may use models to trialfit one or more orthodontic appliances that will be used in the oralcavity to move teeth to desired positions. In other instances, modelsmay be used to pre-position a set of orthodontic brackets and associatedarchwires that are later affixed to the patient's actual dental archesby a technique known as indirect bonding. Models are also used byorthodontists as well as other dental practitioners to serve as apermanent record of a patient's teeth before and after treatment, and insome instances at selected intervals during the treatment program.

[0004] The use of dental models provides significant advantages for boththe dental practitioner and the patient. Models enable the dentalpractitioner to adjust the shape and size of replacement teeth and toothrestorations, to fabricate custom appliances, to adjust the position ofstandard appliances (e.g., indirect bonding), to diagnose patient cases,to plan for oral surgery, and for other like purposes, in thepractitioner's laboratory or in an outside laboratory as desired andduring a time that is most convenient for the dentist or lab personnel.Moreover, such work can be carried out without requiring the patient towait in the dental chair. For example, once a satisfactory fitting ofreplacement teeth, restoration or orthodontic appliances is obtained ona patient model, the replacement teeth, restoration or orthodonticappliances can be readily installed in the patient's oral cavity withfew or no additional adjustments.

[0005] Oftentimes, it has been advantageous to use a mechanical devicecalled an articulator in conjunction with the models to replicatemovement of the patient's lower jaw, i.e., mandible, about the temporalmandibular joint or oral hinge axis. Such articulators include, amongothers, the SAM II brand articulator from Great Lakes Orthodontics, LTD,Buffalo, N.Y.; Hanau articulator available from Henry Shein, PortWashington, N.Y.; articulators available from Whip-Mix Corp. ofLouisville, Ky.; articulators available from Panadent of Grand Terrace,Calif.; as well as the articulator described in U.S. Pat. No. 5,320,528.Articulators are useful for the dental practitioner in the study andcorrection of the patient's occlusion, with the aim of developing theoptimal harmonious occlusal relationship of the patient's dentition. Thearticulator assists in establishing the optimal occlusal relationship byassisting the practitioner in the determination of proper occlusalcontacts and optimum cusp-fossa relationships between the teeth of thepatient's upper and lower jaws.

[0006] In general, conventional articulators use a model of thepatient's upper dental arch and a model of the patient's lower dentalarch. To obtain the models, an impression of the patient's upper dentalarch and lower dental arch is first obtained. To prepare an impressionof the upper arch, a quantity of curable dental impression material isplaced in an impression tray, and the tray is then positioned in thepatient's oral cavity such that the impression material fills andsurrounds the teeth vestibule, and adjacent gingival, i.e., gum, regionsof the upper arch. Once the impression material has cured to asufficient degree, the impression material along with the tray isremoved from the oral cavity. An impression of the patient's lowerdental arch is obtained in a similar manner.

[0007] To make a dental model from each impression, a second curablematerial is poured or otherwise placed in the cured impression material.After the second material has sufficiently cured, the impressionmaterial is removed from the resulting models. When made properly, themodels provide an accurate physical replica of the patient's upper andlower teeth as well as adjacent portions of the patient's gingiva andattachment mucosa.

[0008] In addition to the two dental models, a bite impression of thepatient's upper and lower dental arches is obtained. The bite impressionis often obtained using a wax bite plate. As the patient's dental archesare closed, an impression of the cusps of the upper and lower dentalarches is simultaneously formed on the wax bite plate which serves torecord the relative position between the upper and lower dental archwhen the jaws are closed.

[0009] In addition, a facebow with a bite fork is used to provide arecord of the spatial orientation of the patient's upper dental arch tothe ear canals, the latter of which are located a certain distance fromthe patient's mandibular condyles. One method of using a facebowinvolves placing a compound material such as dental wax or impressionmaterial onto all or a portion of one side of a bite fork. Next, thebite fork is positioned in the patient's oral cavity such that theimpression compound is in secure contact with some or all of the cuspsof the patient's upper teeth to make an impression of such teeth. Next,a facebow is placed into position such that ear pieces of the facebowfit snugly into the patient's outer ear canals. A nasal supportconnected to the facebow is then adjusted so that the facebow liesparallel to the Frankfort horizontal plane at the same time that thenasal support is resting in the Nasian notch with the nasal supportextending along an axis thereof that lies in the patient's sagittalplane.

[0010] Next, the patient's jaws are closed onto the bite fork withsupporting material such that the impression on the upper side of thebite fork is in snug, complemental engagement with the cusps of thepatient's upper teeth. A jig is then connected between the facebow andan arm of the bite fork that extends outwardly from the patient's mouth.The jig includes adjustable connecting arms and couplers which aretightened once the impression on the bite fork is in snug contact withthe cusps of the patient's upper teeth and the facebow has not beeninadvertently moved from its previous position in parallel relationshipto the Frankfort horizontal plane. The bite fork is placed relative tothe upper teeth such that it is used to render an imprint of toothanatomy for relocating the facebow and jig in a mechanical articulatoras described below.

[0011] The facebow with the jig provides a mechanical record of thespatial orientation of the patient's upper dental arch to the patient'sear canals and thus to the patient's mandibular condyles. The facebowand jig can then be used to properly position the model that replicatesthe patient's upper dental arch on the dental mechanical articulator. Insome cases, the articulator may be provided with mounting adapters sothat only the jig and not the facebow is needed to properly position andmount the model of the patient's upper dental arch on the mechanicalarticulator.

[0012] In brief overview, many mechanical articulators include an uppermember and a lower member that are connected together by a pair ofpivotal couplings (such as ball and socket joints). The model of theupper arch is connected to the upper member of the articulator, whilethe model of the lower arch is connected to the lower member of thearticulator. The pivotal couplings enable the two models to move towardand away from each other to mimic at least certain movements of thepatient's jaws.

[0013] To mount the model of the patient's upper dental arch onto thearticulator, the bite fork and the jig (and the facebow in accordancewith some techniques) is connected in secure relationship topredetermined locations of the articulator. The articulator is orientedso that the impressions on the bite fork face in an upwardly direction.Next, the model of the patient's upper dental arch is placed over thebite fork such that the portions of the model replicating the cusps ofthe teeth are in registration with the impressions on the bite fork. Theupper member of the articulator is then brought into position over themodel of the patient's upper dental arch and a quantity of curablematerial is used to fill the space between the model and the uppermember in order to securely connect the same together.

[0014] Next, the bite fork and jig (along with the facebow, if used) isremoved from the articulator and the articulator is inverted. Condylaradjustments are made as necessary to replicate the patient's temporalmandibular joint (TMJ) anatomy and jaw function. The bite impression isthen inverted and placed over the model of the upper arch such that theimpressions of the cusps of the patient's upper teeth are inregistration with the tooth cusps on the model of the patient's upperarch. Subsequently, the model of the patient's lower dental arch isplaced on top of the bite impression such that the tooth cusps of thelower dental arch model are in registration with the bite impression ofthe patient's lower teeth. The upper and lower arch models are heldtogether with elastic elements or modules to stabilize the assembly.

[0015] Another quantity of curable material is then placed in the spacebetween the model of the patient's lower dental arch and the lower armof the articulator. Once the material has hardened, the upper member ofthe articulator is opened so that the bite impression can be removed.Subsequently, the upper member can be moved relative to the lower memberabout the pivotal couplings to replicate opening and closing movement ofthe patient's jaws.

[0016] A variety of mechanical dental articulators are available. Asemi-adjustable hinge articulator is similar to a simple hinge andsimulates only the opening and closing movements of the mandible about asimple hinge axis. Other mechanical articulators are more complex andmay include mechanisms that are adjustable in various planes to simulatelateral and protrusive mandibular movement. Moreover, a variety oftechniques are known for mounting dental models onto mechanicalarticulators, and as such the description set out in the foregoingparagraphs represents only one of many such techniques.

[0017] As can be appreciated, however, the technique of articulationthat is described above is time consuming and must be carefully executedto ensure that the resulting articulation properly simulates motion ofthe patient's jaws. Mechanical articulators are also costly, and themore complex articulators sometimes require factory readjustment toensure that the coupling of the upper member to the lower member of thearticulator is properly calibrated. For these and other reasons, dentalpractitioners typically do not spend the time and expense necessary toarticulate a patient's dental models unless there is a special need forsuch articulation.

[0018] Recently, increased interest has been directed toward obtainingdigitized, three-dimensional images of the teeth and adjacent gingiva ofdental patients. Such images provide an advantage over conventionalplaster of Paris models because the digitized images can be easilystored in a digital file along with other patient information andaccessed as the need arises. For example, an attempt at describing adental model simulator is shown in U.S. Pat. No. 5,338,198 to Wu et al.entitled “Dental Model Simulator,” issued Aug. 16, 1994. Various methodsof obtaining such digitized data have been described, such as laserscanning and photogammetry.

[0019] Another digitization process for obtaining images of teeth isdescribed in pending Israeli Patent Application Serial No. 114691, filedJul. 20, 1995 and entitled “Method and System for AcquiringThree-Dimensional Teeth Image.” This particular illustrative methodacquires a dental image by removing layers of an impression and a dentalimpression tray, or by removing layers of a model made from such animpression. As each layer is removed, a two-dimensional image isobtained by a video camera of the remaining flat surface. Datarepresentative of the boundaries of the two-dimensional imagesrepresenting the surfaces of the teeth and adjacent gingiva are storedby a computing system. Once a sufficient number of layers have beenremoved, the computing system combines the two-dimensional images of thecaptured layers into a three-dimensional created image that representsat least a portion of the patient's teeth and gingiva, e.g., by creatingsurfaces between data points of the captured layers. It should berecognized that such a three-dimensional representation includescalculated data that is generated from actual measured data in thecreation of such surfaces, as opposed to the actual measured data.

SUMMARY OF THE INVENTION

[0020] The present invention is directed toward methods for use indental articulation that overcome the problems noted above with respectto conventional mechanical articulators. With the availability ofdigital dental images, the present invention provides various methodsand programs for use in dental articulation.

[0021] The present invention in its various embodiments is highlyadvantageous for the dental practitioner, because the articulation canbe carried out using a computing system in conjunction with digitaldental image data so that neither models of the patient's upper andlower dental arches nor a mechanical articulator such as described aboveis needed. The present invention enables the practitioner to study thepatient's occlusion so that any necessary corrections can be provided toestablish proper occlusal contacts and optimum cusp/fossa relationshipsbetween the teeth of the patient's upper and lower dental arches as wellas providing other advantages that will be apparent to one skilled inthe art from the description provided herein.

[0022] A computer implemented method of creating a dental model for usein dental articulation according to the present invention includesproviding a first set of digital data corresponding to an upper archimage of at least a portion of an upper dental arch of a patient,providing a second set of digital data corresponding to a lower archimage of at least a portion of a lower dental arch of the patient, andproviding hinge axis data representative of the spatial orientation ofat least one of the upper and lower dental arches relative to a hingeaxis of the patient. Bite alignment data representative of the spatialrelationship between the upper dental arch and the lower dental arch ofthe patient is further provided and the upper arch image and the lowerarch image are aligned based on the bite alignment data. A referencehinge axis is created relative to the aligned upper and lower archimages based on the hinge axis data.

[0023] In one embodiment of the method, the method further includesproviding data associated with condyle geometry of the patient. Suchcondyle geometry data provides limitations on the movement of at leastthe lower arch image when the arch images are displayed and manipulatedto move at least the lower arch image relative to the upper arch imageand the reference hinge axis.

[0024] In another computer implemented method of creating a dental modelfor use in dental articulation, the method includes providing a firstset of digital data corresponding to an upper arch image in a coordinatesystem of at least a portion of an upper dental arch of a patient,providing a second set of digital data corresponding to a lower archimage in the coordinate system of at least a portion of a lower dentalarch of the patient, and providing hinge axis data representative of thespatial orientation of at least one of the upper and lower dental archesrelative to a condylar axis of the patient. A reference hinge axis iscreated in the coordinate system relative to the upper and lower archimages based on the hinge axis data.

[0025] In yet another computer implemented method of creating a dentalmodel for use in dental articulation, the method includes providing afirst set of digital data corresponding to an upper arch image of atleast a portion of an upper dental arch of a patient, providing a secondset of digital data corresponding to a lower arch image of at least aportion of a lower dental arch of the patient, and providing bitealignment data representative of the spatial relationship between theupper dental arch and the lower dental arch of the patient. The upperand lower arch images are moved relative to one another based on thebite alignment data until an aligned upper and lower arch image isattained. Thereafter, the aligned upper and lower arch images are movedtowards each other until a first contact point is detected. At least oneof the upper and lower arch images are then moved relative to the otherin one or more directions to a plurality of positions for determiningoptimal occlusion position of the lower and upper dental arches.

[0026] A computer implemented method of dental articulation is alsodescribed. The method includes providing a dental articulation model.The model includes a first set of digital data corresponding to an upperarch image of at least a portion of an upper dental arch of a patient, asecond set of digital data corresponding to a lower arch image of atleast a portion of a lower dental arch of the patient, and a third setof digital data representative of the spatial orientation of the upperand lower arch images relative to a reference hinge axis. At least theupper and lower arch images are displayed based at least on the firstand second sets of digital data and one or more of the first, second,and third sets of digital data are manipulated to move at least one ofthe upper and lower arch images about the reference hinge axis tosimulate movement of the upper and lower dental arches of the patient.

[0027] In one embodiment of the method, the model further includes afourth set of digital data representative of the spatial orientation ofcondyle geometry of the patient relative to the reference hinge axis.The manipulation of the digital data may then include manipulation ofone or more of the first, second, third and fourth sets of digital datato move at least the lower arch image relative to the upper arch imageand the reference hinge axis.

[0028] In another computer implemented method of dental articulation,another set of digital data representative of an image having at leastthree points corresponding to at least three identifiable points of thedental articulation model is provided. At least a portion of the dentalarticulation model registered with the image is displayed based at leastin part on the additional set of data. For example, the set of digitaldata may be representative of any two dimensional or three dimensionalimage.

[0029] In yet another computer implemented method of dentalarticulation, yet another set of digital data may be provided which isrepresentative of a plurality of motion recordings of the patient'smandible. The dental articulation model is manipulated to move the lowerarch image to simulate relative movement of the lower arch of thepatient based at least on the fourth set of digital data.

[0030] A computer readable medium tangibly embodying a programexecutable for creating a dental model for use in dental articulation isalso provided along with a computer readable medium tangibly embodying aprogram executable for performing dental articulation. A facebowapparatus for use with the present invention is also described. Otheraspects and further details of the present invention are set out in thedescription below as well as in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is block diagram of a dental articulation model creationprogram in conjunction with a user program for use of a dentalarticulation model created by the model creation program.

[0032]FIG. 2 is a more detailed block diagram of the dental articulationmodel creation program of FIG. 1.

[0033]FIG. 3 is a block diagram of an interconnected system for creationof a dental articulation model and for use of the dental articulationmodel; the system includes memory for storing the programs showngenerally in FIG. 1.

[0034]FIG. 4 is a more detailed diagram of an alignment portion of thedental articulation model creation program of FIG. 2.

[0035]FIG. 5 is more detailed diagram of a hinge axis attachment portionof the dental articulation model creation program of FIG. 2.

[0036] FIGS. 6A-6B show one embodiment of a method for providing bitealignment data for use by the dental articulation model creation programshown in FIG. 1 along with an embodiment of an alignment method usingsuch bite alignment data.

[0037]FIG. 7 is another embodiment of a method for providing bitealignment data for use by the dental articulation model creation programshown in FIG. 1 along with an embodiment of an alignment method usingsuch bite alignment data.

[0038]FIG. 8 is one embodiment of a method for providing hinge axis datafor use by the dental articulation model creation program shown in FIG.1 along with an embodiment of an attachment method using such hinge axisdata.

[0039]FIG. 9 is another embodiment of a method for providing hinge axisdata for use by the dental articulation model creation program shown inFIG. 1 along with an embodiment of an attachment method using such hingeaxis data.

[0040]FIG. 10A shows a flow diagram of a bite registration algorithm foruse in providing optimal occlusal relationship in accordance with thepresent invention and

[0041]FIGS. 10B and 10C show screen displays for use in describing thealgorithm.

[0042] FIGS. 11A-11C illustrate a facebow apparatus for providing hingeaxis data for use by the dental articulation model creation programshown in FIG. 1.

[0043]FIG. 11A is a top view of the apparatus;

[0044]FIG. 11B is a front view of the apparatus, and

[0045]FIG. 11C is a side view of the apparatus.

[0046]FIGS. 12A and 12B are illustrations of a graphic user interfaceprovided by the dental articulation program of FIG. 1.

[0047]FIG. 13 is a block diagram illustration of the attachment ofadditional files to the dental model according to the present invention.

[0048]FIG. 14 is one embodiment of a method for attaching a graphicsfile representative of an image to the dental model along with use ofsuch attached data.

[0049]FIG. 15 is another embodiment of a method for attaching a fileincluding motion data to the dental model along with use of suchattached data.

[0050]FIGS. 16A and 16B are graphic user interface illustrations showingthe display of information of the graphics file resulting from themethod of FIG. 14.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] The present invention shall be described generally with referenceto FIGS. 1-5. Thereafter, the present invention shall be described infurther detail with reference to FIGS. 6-16.

[0052] As used herein, the terms given below are defined as follows.Bite registration is defined as the location of the upper and lowerdental arches of a patient in occlusion (e.g., maximum intercuspation).The occlusal relationship may be based on first point of contact orbased on other degrees of interdigitation of the upper and lower dentalarches such as interdigitation for providing maximum intercuspation orto a controlled point of contact between the upper and lower dentalarches which avoids mandibular shifting (e.g., shifting which may be dueto occlusal prematurity).

[0053] Articulation is defined as bite registration in addition to therelationship of the upper and lower dental arches to the condyle axis ofthe patient. Articulation may occur either as simple hinge motion (i.e.,simple hinge articulation) about the condyle axis or hinge motion incombination with other motions of the lower arch relative to the upperarch allowed by the condyle geometry of the patient and muscle function(e.g., full articulation in its most complex form allows for allrotational motion and translational motion of the lower arch relative tothe upper arch as would be possible in a patient). In other words, withthe upper arch being a rigid body connected to the fossas of thepatient's cranium and the lower arch being a rigid body connected to thecondyles of the patient's mandible, such complex articulation mayinclude all motions (e.g., rotational and/or translational) possible ofthe mandible relative to the cranium (e.g., 6 degrees of freedom).Articulation may be described using relationships with externalreferences such as, for example, a horizontal reference plane (e.g., theFrankfort horizontal) and/or a vertical reference plane (e.g., sagittalplane).

[0054] Also as used herein, measured digital data refers to digital datacaptured directly from a patient's anatomy in a digital form (e.g.,teeth, gums, condyle geometry, etc.) by any method (e.g., stereographs,digitization probes, optical scanning and detection devices, etc.) orcaptured indirectly from a patient by removing information regarding thepatient's anatomy in a nondigital form (e.g., dental impressions, studymodels, x-rays, etc.) and then digitizing such information by any method(e.g., slicing the impressions and digitizing boundaries, using anoptical scanning and detection device, etc.). Calculated digital data,on the other hand, as used herein refers to digital data generated frommeasured digital data or any other data. Three-dimensional surface datagenerated using measured digital data is one example of calculateddigital data.

[0055]FIG. 1 shows a dental articulation model creation program 10 inconjunction with a user program 20. The model creation program 10 isprovided with input data. Such input data at least in part includesdigital dental arch data 14 representative of upper and lower dentalarches of a patient, bite alignment data 16 representative of therelationship of the upper and lower dental arches of a patient, andhinge axis data 18 representative of the relationship between the upperand/or lower dental arches of the patient and the condyle axis of thepatient. Further, condyle geometry digital data 19 representative ofcondyle geometry of the patient may also be used as further describedherein. The model creation program 10 uses this input data to create adental articulation model 11 which is the output of the dental creationmodel program 10. The dental articulation model 11 includes at leastdata representative of images of the upper and lower dental arches ofthe patient as provided by the dental arch data 14, and relational datarepresentative of the spatial relationship of the dental arch images toone another and further representative of the spatial relationship ofthe arch images relative to a reference hinge axis corresponding to thecondyle axis of the patient. The relational data is determined based onthe dental arch data 14, the bite alignment data 16, and the hinge axisdata 18.

[0056] In many cases, complete orthodontic diagnosis requires detailedknowledge of the geometry of the teeth and soft tissue, i.e., gingiva,that constitute each of the upper and lower dental arches of thepatient; the relationship of the dental arches to one another; therelationship of the upper and lower arches to the condyle axis; and therelationship of the dental arches to the skull or parts thereof.Further, the orthodontist may wish to consider the specific geometry ofthe patient's condyle and the effects of that geometry on the movementof the mandible of the patient. As opposed to the conventional method ofrepresenting such information to the orthodontist, i.e., using physicaldental models mounted in a mechanical articulator, the present inventioncaptures such information as digital data in the dental articulationmodel 11 and presents such information to the user, e.g., orthodontist,in displayed three-dimensional image(s), two dimensional view(s), and/ortwo dimensional projection(s).

[0057] Once created, the dental articulation model 11 can be used topresent images of the patient's upper and lower dental images, orportions thereof to the user by dental articulation user program 20. Forexample, the user program 20 can be used to manipulate the displayedarticulation model in any manner as would be known to one skilled in theart, and further as specifically described herein. For example, the userprogram 20 may include routines for performing measurements withreference to the model, routines for manipulation of the orientation ofthe model as a whole (e.g., the perspective view of all displayedelements being moved in space together), routines for rotating the lowerdental arch image relative to a fixed upper dental arch image about areference hinge axis, routines for movement of the upper dental archimage relative to the reference hinge axis or the lower dental archimage, routines for translational movement of one of the dental archimages as allowed by the condylar geometry of the patient, or routinesfor detecting virtual contact of one dental arch image with respect toanother. It should be apparent to one skilled in the art that thecapabilities for movement of objects displayed by a computing system arevirtually unlimited and the present invention is not to be limited byany particular user application routine described specifically herein.

[0058] Generation of the virtual articulation model 11 generallyinvolves gathering and digitization of the necessary information andthereafter creating the model 11 from such gathered information. Thegathering of the necessary information is shown in FIG. 1 as blocks 14,16, 18 and 19. This information is the input data to the dental creationmodel program 10.

[0059] First, as generally shown by block 14, the data collectionprocess includes capturing the three dimensional morphology of theindividual dental arches of the patient. Preferably, such data includesdata representative of the structure of all the teeth and the relevantgingiva, but the present invention is also of benefit when one or moreportions of such dental arches are captured, e.g., one or more teeth ina section of one of the dental arches. There are a variety of methodsavailable for providing such information and the present invention isnot limited to any particular method but only as described in theaccompanying claims. For example, tools which can be utilized to providemeasured digital data representative of the upper and lower dentalarches may include dental impressions, laser scans, stylus scans, and/orstereophotographs. The measured digital data concerning the upper andlower dental arches may be captured directly from the patient in adigital form, e.g., stereographs, or the information may be capturedindirectly from the patient by removing the information from the patientin a nondigital form (e.g., dental impressions and study models) andlater digitizing the information (e.g., slicing the dental impressionsand digitizing the boundaries). Some of the varied processes forproviding digitized data of dental arches include, but are clearly notlimited to, laser scanning, photogammetry, and those processes describedin U.S. Pat. Nos. 5,078,599, 5,131,844, 5,338,198, 4,611,288, 5,372,502,Article entitled “Three-dimensional dental cast analyzing system withlaser scanning,” by T. Kuroda, et. al., Am.J.Ortho.Dent.Othrop.,Vol.110[4], October 1996, pp. 365-69, and Israeli Patent ApplicationSerial No. 114691 previously cited herein. Preferably, the digital datarepresentative of the dental arches of a patient is provided by theprocess described in Israeli Patent Application Serial No. 114691resulting in measured digital data representative of boundaries ofsliced portions of dental impressions. Further, such digital data mayinclude calculated data representative of surfaces of the dental archesas opposed to the measured digital data. Such calculated digital datafor display of surfaces can be generated in numerous ways from themeasured digital data as would be known to one skilled in the artresulting in data representative of various elements used for display ofsuch surfaces, e.g., various calculated points, meshes, polygons, etc.

[0060] Second, as generally shown by block 16, the data collectionprocess includes measuring the spatial relationship between the upperand lower dental arches of the patient to provide the bite alignmentdata necessary to create the dental articulation model 11. There are avariety of methods available for providing such information and thepresent invention is not limited to any particular method but only asdescribed in the accompanying claims. For example, one method mayinclude identifying at least three nonlinear points on each dental archand measuring matched pairs of such points, i.e., a pair being one pointfrom each arch. Such measurements may be obtained directly from thepatient, i.e., in vivo, or from representations of the dental arches ofthe patient, such as impressions of the dental arches or dental studymodels. As another example, alignment features may be added to a modeland thereafter digitized with the digitization of the dental arches ofthe patient. For example, the feature may include one or more points,lines, or planes having common features extending from one dental archto another. Another tool that may be beneficial for obtaining suchinformation may be a bite impression, such as a silicone or wax biteimpression. Further, electronic transducers with digital output are alsoavailable such as an instrumented bite fork available under the tradedesignation of T-Scan from Tekscan, Inc. (Boston, Mass.).

[0061] The digital data representative of the dental arches as providedin block 14 and the information defining the relationship between sucharches as provided in block 16 can also be captured simultaneously. Forexample, the arch morphology and the relationship between the arches maybe simultaneously captured with use of a double impression. In otherwords, a double impression may be taken from the patient and thereafterdigitized, such as with use of the method described in Israeli PatentApplication Serial No. 114691. Several processes for providing such bitealignment data (block 16) will be described further below along with themanner in which the dental model creation program 10 uses such data tocreate the dental articulation model 11.

[0062] Third, as generally shown by block 18, the data collectionprocess includes capturing the spatial relationship between the upperand lower dental arches of the patient and the condyle axis of thepatient to provide the hinge axis data necessary to create the dentalarticulation model 11. There are a variety of methods available forproviding such hinge axis data and the present invention is not limitedto any particular method but only as described in the accompanyingclaims. For example, one method may include identifying and measuringthe location of at least three nonlinear points on the dental archesrelative to the condyle axis. Further, for example, this relationshipmay be obtained through measurements including facebow transfers (FIGS.11A-11C) or obtained through the use of cephalometric x-rays. Severalprocesses for providing such hinge axis data (block 16) will bedescribed in more detail below along with the manner in which the dentalmodel creation program 10 uses such data to create the dentalarticulation model 11.

[0063] Optionally, and finally, condyle geometry data may be provided asgenerally shown by block 19. Condyle geometry can be determined byvarious registrations (e.g., images, measurements, etc.) of lateral andprotrusive excursions of the mandible of the patient and may takevarious forms. As there are a variety of methods available for providingsuch information, the present invention is not limited to any particularmethod but only as described in the accompanying claims.

[0064] For example, condyle geometry data 19 may take the form ofcalculated geometric data of the condyles. Calculated condyle geometrymay be created in manners similar to those used for preparing such datafor conventional mechanical articulators; many of such techniques beingknown to those skilled in the art. For example, cephalometric x-rays,tomograms, or magnetic resonance images can be used to obtain such data,as well as methods such as those described in U.S. Pat. No. 4,681,539 toKnap which include forming three dimensional physical recordings (i.e.,models) that represent the condyle geometry and which are use in amechanical articulator to control the motion of physical models of theupper and lower dental arches. Such physical condyle geometry models asdescribed in Knap may be digitized into three dimensionalrepresentations of the condyle geometry for use in the present inventionas the condyle geometry data 19. Alternatively, the elements of Knapwhich allow for formation of the physical recordings of the condylegeometry may be replaced with a three dimensional position sensor todigitize the condyle geometry directly as opposed to after the physicalrecordings of the condyle geometry data are generated. The calculatedcondyle geometry data may be easily attached, i.e., linked, to thedental articulation model as both include common condyle axisinformation. Such calculated condyle geometry data provides for limitson the motion of the upper and lower dental arch images of the dentalarticulation model. For example, motion of such images may be confinedto the condyle geometry.

[0065] In addition, other data may be used in conjunction with thedental model such as data resulting from recording appropriate motionsof the patient during activation of the patient's mandible as describedhere and in further detail below. At a minimum, such recorded motionsmay consist of a series of three dimensional positions of three pointsof the mandible while the maxilla is held in a known fixed position.Such recordings may be made using an Axiograph from Great LakesOrthodontics of Buffalo, N.Y. or a Sirognathograph from Siemens ofBensheim, Germany. The recorded motions may be captured in computerstorage files attached and linked through the common condyle axis to thedental articulation model. The recorded motions can then be played backto show full articulation. The motion files can be supplemented withobservational files which may indicate joint clicking and otherobservations made by a user. The advantage of this recorded motiontechnique is that geometrical calculation of the condyles is avoided.Further, preservation of the actual movements of the patient's mandiblemeans that all the available information is captured for later analysis.Also, since the dental articulation model is a three-dimensionalcomputer model, the motion of any point on the full articulator can becalculated from the three known points. Therefore, one can calculate anddisplay the traditional pantographic tracings from the three dimensionalmotion measurements.

[0066] Further, excursion information from a base position can be usedto capture changes in geometrical relationships of the condyle geometry.For example, the geometrical relationships between the condyle and thefossa can be captured (e.g., by x-ray). The excursion information canthen be used to calculate the motion of the condyle in the fossa. Thismotion information can be used to animate the condyle and fossa image.

[0067] With the provision of digital data representative of the upperand lower dental arches 14, the provision of the bite alignment data 16,the provision of the hinge axis data 18, and the provision of theoptional condyle geometry data 19, the dental creation model program 10is used to create the dental articulation model 11. As shown in furtherdetail in FIG. 2, the dental articulation model creation program 10includes alignment routines 22 and hinge axis attachment routines 24 forproviding a model suitable for use in simple hinge articulation.Further, FIG. 2 shows in further detail the inclusion of optionalcondyle geometry attachment routines 25 for providing a model suitablefor use in full articulation.

[0068] Alignment routines 22 manipulate the measured digital data toalign the digitized images of the upper and lower dental arches providedper block 14. Generally, as shown in FIG. 4, the digital images (e.g.,three dimensional graphic images) are input (e.g., imported from anotherprogram) for use by the model creation program 10. The digital datarepresentative of the upper and lower dental arch images is manipulated,e.g., the images translated and rotated, until proper alignment betweenthe upper and lower images is indicated as defined by the bite alignmentdata (block 16). Further, the measured digital data is manipulated forproviding bite registration, i.e., the location of the upper and lowerdental arches of the patient in occlusion. Thereafter, the informationdescribing the relationship between the upper and lower dental arches issaved.

[0069] Further, as shown in FIG. 4, optionally, the alignment routines22 may include a centric occlusion bite registration algorithm 23(described in further detail below with reference to FIGS. 10A-10C) tooptimize the position of the upper and lower members in centricocclusion. Portions of the centric occlusion bite registration algorithm23 provide routines for providing a technique referred to hereinafter asthe wobbling technique. Generally, the wobbling technique provides formanipulation of the measured digital data representative of the upperand lower dental arches to move the upper and lower dental archesrelative to one another in one or more different directions byrelatively small increments, e.g., one or two pixel increments, tooptimize the occlusal relationship between the upper and lower dentalimages. For example, optimal occlusal relationship may include thelocation of the upper and lower dental arches in maximum or near maximumintercuspation. Further, generally, the wobbling technique is a digitalform of processes used in making small adjustments in a mechanicalarticulator such as when fitting two physical models of the mechanicalarticulator together. It should be recognized that the centric occlusionbite registration routines are preferably performed using measureddigital data as opposed calculated digital data. Thus, the optimizedposition of the lower and upper dental arches is based on actualmeasured data as opposed to calculated data generated using suchmeasured data. Calculated data, e.g., generated surface data, mayinclude undesirable additional tolerances from the actual anatomy of thepatient.

[0070] After the upper and lower dental images have been alignedrelative to one another (block 22), the hinge axis attachment routines(block 24) are used to define the spatial relationship between thedental arch images as represented by the digital data of such images(block 14) and the condyle axis of the patient. As shown in the moredetailed diagram of FIG. 5, the digital data representative of the upperand lower arch images as aligned and stored (block 22, FIG. 4) isprovided as the input to the hinge axis attachment routines 24. Thehinge axis data (block 18) is then use to locate a reference hinge axisfor the dental articulation model 11 relative to the aligned upper andlower dental arch images. Thereafter, digital data representative of thereference hinge axis is linked or attached to the digital data createdand stored by the alignment routines (block 22) and the dentalarticulation model is stored for further use by the user program 20.

[0071] Further, as shown in FIG. 2, the optional condyle geometryattachment routines 25 provide for linking the condyle geometry data 19to the portions of the dental articulation model as generated byalignment routines (block 22) and hinge axis attachment routines (block24). Generally, the reference hinge axis of the patient has already beenspatially defined in the dental articulation model relative to the upperand lower dental arches. With the condyle axis of the patient beingknown in the condyle geometry data (block 19), such condyle geometrydata 19 can be spatially attached to the dental articulation model usingthe common condyle axis (i.e., reference hinge axis) feature alreadyspatially defined relative to the upper and lower dental arches. Thecondyle geometry data 19 may define the limits through which the upperand lower dental arch images can be moved during manipulation by a user.For example, lateral and protrusive excursions of the lower arch may beconfined to within the limits of the condyle geometry data as providedin block 19 for the patient. The linked optional condyle geometry datais thus stored in conjunction with the other elements of the dentalarticulation model 11 for further use with user program 20.

[0072] At a minimum, the stored dental articulation model 11 (after thelower and upper arches have been aligned and the hinge axis attached)for simple hinge articulation includes a file structure that describesat least a line corresponding to the condyle axis of the patient (e.g.,the line may be represented by end points of the line representative ofthe center of the condyles) and at least three nonlinear pointscorresponding to an object rotatable about the condyle axis in the samecoordinate system as the condyle axis, e.g., the object being the lowerdental arch.

[0073] Preferably, the dental articulation model 11 includes a filestructure that describes at least a line corresponding to the condyleaxis of the patient, at least three nonlinear points corresponding tothe lower dental arch in the same coordinate system as the condyle axis,and at least three nonlinear points corresponding to the upper dentalarch in the same coordinate system as the condyle axis.

[0074] More preferably, the dental articulation model 11 includes a filestructure that describes at least a line corresponding to the condyleaxis of the patient, points more fully describing the lower dental archin the same coordinate system as the condyle axis (e.g., pointscorresponding to the measured digital data of the objects such as thedigitized boundaries of the sliced impressions), and points more fullydescribing the upper dental arch in the same coordinate system as thecondyle axis.

[0075] Yet more preferably, each of the file structures above mayfurther optionally include the condyle geometry data generated for thepatient and which lies in the same coordinate system as the condyleaxis. With the dental articulation model 11 including the condylegeometry data, full articulation can be performed when the model is usedin conjunction with the user program 20.

[0076] One example illustrative of a file structure that describes adental articulation model 11 is set forth below. In general with respectto the data format, all data in the file structure is standard ASCIIcharacters; all data is organized in lines, terminated with “\n”; thefirst word in a line is usually the key word associated with the line;some lines do not have keywords, only data; key words that are notrecognized are ignored; and lines with text data begin with a colon (:).

[0077] Further, the file structure may include two versions of headers:short and long headers. The short header consists of one type of entity:BoundBox. The keyword “BoundBox” is followed by two corners of thebounding box in x, y, z floats. The long header includes various items:

[0078] First line: consists of at last the version of the filestructure.

[0079] Data lines: each data line begins with a key word; data dependson the keyword; unrecognized keys may be ignored.

[0080] Data Items:

[0081] BoundBox: the keyword “BoundBox” is followed by two corners ofthe bounding box in x, y, z floats.

[0082] Program: the version of the creating program is written.

[0083] BL: the name of the BL file used to create this 3D file.

[0084] Terminating line: End Header

[0085] The file structure is divided into several layers. The layers arenumbered 0-5 with each layer used to store some graphic elements. Forexample, the layer 10 may include the contour base data of the dentalmodel (e.g., measured digital data such as the digitized boundaries aspreviously described herein which form contours if displayed); layer 11may include draft version of 10; layer 12 may be a low resolution grid(e.g., calculated digital data based on the measured digital data suchas meshes); and layers 13-14 may be higher resolution grids.

[0086] The various graphic elements may include, for example, threedimensional lines, meshes, and objects; the three dimensional objectsmay include, for example, object data lines describing control polygons,object sections, point meshes, and point clusters, for use in describingobjects such as the lower/upper dental arch, teeth, condyle geometry,etc. Such graphic elements may be provided as follows:

[0087] 3d Polyline:

[0088] First line: the keyword “Poly3”.

[0089] Data lines: a list of 3D polyline points, each point in one line.

[0090] Terminating line: the list is ended by an “EndPoly” statement.

[0091] 3d Mesh:

[0092] First line: the keyword “Mesh n m” where n and m are the numberof mesh points in x and y directions; this object is a rectangular arrayof 3D points, interpolated by bilinear interpolation.

[0093] Data lines: flag, x, y, z; if flag is 0, the point data is notdisplayed (i.e., a hole in the mesh).

[0094] Terminating line: ended by an “EndMesh” statement.

[0095] 3d Object (such as Lower/Upper arch, teeth, etc.): each objectcan contain several items of data.

[0096] First line: Object obj_name; the 3d Object keyword starts anobject; for example, special obj_names are lower_arch (for the lowerdental arch) and upper_arch (for the upper dental arch).

[0097] Object data lines:

[0098] Control Polygon:

[0099] First lines: ControlPolygon

[0100] Data lines: x y z; where x, y, and z are floating pointcoordinates of the control polygon.

[0101] Last line: EndPoly

[0102] Data section (a part of a data polyline):

[0103] Data Line: Section cont_num starting_point ending_point;following the keyword section the three integer items refer to a set ofpoints; point are to be taken from a contour (data polygon) cont_num,starting at point starting point up to (and including) ending_point.

[0104] List of Data sections:

[0105] First line: Sections

[0106] Data Line: cont_num starting_point ending_point; points are to betaken from a contour (data polygon) cont_num, starting at pointstarting_point up to (and including) ending_point.

[0107] Last line: EndSections

[0108] Point mesh:

[0109] First line: ‘Mesh n m’, where n and m are the number of meshpoints in x and y directions; this object is a rectangular array of 3Dpoints, interpolated by bilinear Interpolation.

[0110] Data lines: flag x y z; if flag is 0, the point data is notdisplayed (a hole in the mesh)

[0111] Terminating line: EndMesh

[0112] Point cluster (unordered points): this data item contains a setof points and optionally a list of edges and list of faces.

[0113] First line: PointCluster n, where n is the number of points inthe cluster.

[0114] Data lines: x y z, where x, y and z are 3D coordinates of thepoints.

[0115] Separator line: Edges n, where n is the number of edges in thecluster.

[0116] Data lines: i j; an edges goes from point i to point j.

[0117] Separator line: Faces n, where n is the number of faces in thecluster.

[0118] Data lines: i j k l m n; all items are integer indexes of pointssurrounding a face.

[0119] Terminating line: EndCluster

[0120] Object's Termination line: EndObject

[0121] The illustrative file structure will also describe the referencehinge axis, i.e., condyle axis, in the same coordinate system as theother objects of the file structure. The condyle axis defines the axisof rotation of the lower dental arch (object lower-arch) relative to theupper dental arch (object upper arch). The condyle axis may consist of akey word “tmj_axis” followed by six numbers; the first three numbersdefine one end point of the axis and the last three numbers define theother end point of the axis. Example: tmj_axis p1 p2 p3 p4 p5 p6.

[0122] Further, the illustrative file structure may also describe thecondyle geometry in the same manner as the other three-dimensionalobjects (e.g., dental arches) as described above. Other nongraphicelements may also be included in the file structure. For example, onetype of nongraphic element is text.

[0123] It will be readily apparent to one skilled in the art that thefile structure for the dental articulation model may take many differentforms so long as the desired information necessary for performing simplehinge articulation or full articulation as desired is available for useby user program 20. For example, the file structure may include two ormore file structures linked to one another. Further, such file structuremay also include attached graphical files such as data from acephalometric x-ray as further described below or a file of recordedmandibular motion for use in playback of mandibular motion using thedental model as further described below.

[0124] As shown in the diagram of FIG. 3, the dental creation program 10may be resident in memory 34 of a first computing system 30 and the userprogram 20 may be resident in memory 44 of another computing system 40.However, as would be apparent to one skilled in the art, the programs 10and 20 may be resident in the memory of the same or different computingsystems. It is also readily apparent that the present invention may beadapted to be operable using any processing system, e.g., personalcomputer, and further, that the present invention is in no mannerlimited to any particular processing system. The amount of memory of thesystems should be sufficient to enable the user to allow for operationof the programs 10, 20 and store data resulting from such operation. Itis readily apparent that such memory may be provided by peripheralmemory devices to capture the relatively large data/image filesresulting from operation of the systems. The systems 30,40 may includeany number of other peripheral devices as desired for operation of thesystems 30, 40, such as, for example, the following respective devices:display 38, 48; keyboard 37, 47; and mouse 35, 45. However, it isreadily apparent that the system is in no manner limited to use of suchdevices, nor that such devices are necessarily required for operation ofthe systems 30, 40.

[0125] For example, the computing system 30, 40 may be an HP Vectra-VLwith a Matrox Millenium Graphics Card or may be a Netpower Symetra-IIwith a True-TX Prographics card. However, any suitable computing systemmay be used. Various programming languages may be used to accomplish thefunctions as described herein as would be readily apparent to oneskilled in the art. For example, such functionality may be providedusing C++ language. Further, available software packages may be used forproviding various functions as described herein. For example, OpenInventor available from Silicon Graphics may be used to display thedental articulation model to a user. In addition, information may bestored and communicated using digital diagnostic protocol (DDP),commonly known to those skilled in the art.

[0126] As shown by the generalized interconnection 31, the informationavailable in either system may be transmitted for use by the other. Thisinterconnection leads to a process that can be implemented for use by auser in a relatively quick manner. For example, the dental articulationmodel may be created at one location (e.g., such as a lab whereimpressions are digitized) and thereafter be transmitted back to adental office for use by an orthodontist; hinge axis data (e.g., such asobtained through a facebow apparatus) may be transmitted to a lab foruse in creating the model; or various routines for manipulating themodel may be downloaded for use by the user.

[0127] Although FIGS. 1 and 2 show the alignment routines 22 and hingeaxis attachment routines 24 as being part of a single program andoperable as part of a particular computing system, it should be readilyapparent that various portions of the program may be resident atmultiple locations and various functions carried out at such multiplelocations. For example, the hinge axis attachment routines 24 may beresident on a computing system at a user's location. With such aconfiguration, the alignment may be performed at a first location withthe user providing the hinge axis data for input to the system at theuser's location. As such, if the hinge axis data is obtained with use ofa facebow apparatus, (e.g., such as an apparatus as described herein)the user may input such hinge axis data into the hinge attachmentroutines of which the alignment data is also an available input. Thedental articulation model may then be created immediately at the user'slocation. The user then has immediate access to a dental articulationmodel created for a patient.

[0128] Various embodiments of processes used in accordance with thepresent invention shall be further described in more detail withreference to FIGS. 6-16. It should be readily apparent that suchembodiments are only illustrative of the various methods which may beused for performing functions in accordance with the present invention.As such, the present invention is not limited to any particularillustrative embodiment as described herein, but only as described inthe accompanying claims.

[0129]FIG. 6 and FIG. 7 show two illustrative embodiments for providingbite alignment data (block 16) according to the present invention. Inaddition, the FIGS. 6 and 7 show at least portions of the alignmentroutines (block 22) for aligning the upper and lower arch images usingbite alignment data provided in the respective illustrative manners.

[0130] As shown in the embodiment of FIG. 6A, provision of bitealignment data includes taking impressions and pouring upper and lowerarch models of the upper and lower dental arches of a patient. Further,a bite registration impression, e.g., a wax bite registration, is takenof the patient. The upper and lower arch models are physically alignedusing the bite impression positioned therebetween. With the upper andlower arch models maintained in physical alignment with the biteimpression, at least one feature common to both the upper and lowerdental arch models is trimmed or otherwise formed in the models. Thecommon feature provides the relationship between the upper and lowerarch models. For example, the feature may be a line and a planeperpendicular to the occlusal plane, or any other suitable feature orfeatures.

[0131] Thereafter, a digital representation of the dental arch modelsincluding the alignment feature created in each of the upper and lowerdental arches is generated. For example, the digital representation maybe provided using any one of the processes as described above as wouldbe known to one skilled in the art.

[0132] With the digital data representative of the upper and lowerdental arches provided to the model creation program 10 along with thebite alignment data in the form of the digitized alignment feature, thealignment routines 22 are performed as follows. As shown in the displaydiagram of FIG. 6B, the common features across the upper and lowermodels is a line segment 52 and a back plane 54 which includes an upperarch back plane 56 and a lower arch back plane 58. With the digitalimages (including the digitized common feature) input to the alignmentroutines 22, a point is chosen and the upper arch back plane 56 isplaced such that the point is part of the plane 56. Thereafter, theposition of the upper back plane 56 is recognized by the program and thelower arch back plane 58 is brought into the same plane as plane 56.With the back planes 56 and 58 aligned, the routines 22 recognize thecoordinates of the line segment 52 in the upper back plane 56 and linesegment of the lower back plane 58 is aligned with the coordinates. Assuch, the upper and lower dental images are registered to one another.This aligned data is then stored for use by the hinge axis attachmentroutines 24.

[0133] As shown in FIG. 7, provision of bite alignment data (block 16)includes capturing the spatial coordinates (x, y, z) of at least threeidentifiable nonlinear points in each of the upper and lower dentalarches of the patient (e.g., incisor cusp tip, pits on left and rightsecond molars, etc.). For example, such spatial coordinates may beobtained using a digitizer from Immersion Corp. sold under the tradedesignation of Microscribe-3DX digitizer and which is equipped with astylus tip. The spatial coordinates can be captured directly from thepatient or from a representation of the patient that contains therelationship of the upper and lower dental arches, e.g., a wax biteimpression.

[0134] With the digital data representative of the upper and lowerdental arches provided to the model creation program 10 along with thespatial coordinates of the at least three nonlinear points in each ofthe upper and lower dental arches of the patient, the alignment routines22 are performed as follows. The digital data representative of theupper and lower dental arches is manipulated such that correspondingpoints of the upper and lower arch images represented by the digitaldata are in the same spatial relationship as the spatial coordinates ofthe bite alignment data. In other words, the identifiable points of theupper and lower dental arches of the patient as provided by the bitealignment data and the corresponding identifiable points of the dentalarch images are aligned.

[0135]FIG. 8 and FIG. 9 show two illustrative embodiments for providinghinge axis data (block 18) according to the present invention. Inaddition, the FIGS. 8 and 9 show at least portions of the hinge axisattachment routines (block 24) for attaching the reference hinge axis tothe aligned upper and lower arch images using hinge axis data providedin the respective illustrative manners.

[0136] As shown in FIG. 8, provision of hinge axis data (block 18)includes taking at least a lateral cephalometric x-ray of the patient.The lateral x-ray is taken perpendicular to the condyle axis. The centerof the condyle, i.e. the condyle axis, is located on the x-ray. Twoidentifiable points, i.e., landmarks (e.g., incisor cusp tip, distalsurface of the second molar, etc.), on the upper or lower arches arelocated on the x-ray which have corresponding points that can also beidentified on a buccal view of the upper and lower arch images providedby the digital data representative of the upper and lower dental archesof the patient (block 14). The x, y coordinates of the two identifiablepoints are then measured relative to the center of the condyle, i.e.,condyle axis, and provided as the hinge axis data to be used by thedental model creation program 10.

[0137] With the digital data representative of the upper and lowerdental arches provided to the model creation program 10 along with thehinge axis data, i.e., the x, y coordinates of the identifiable points,the hinge axis attachment routines 24 are performed as follows. Thedigital data representative of the upper and lower dental arches ismanipulated such that the upper and lower dental arch images representedby the digital data are represented in a buccal view corresponding tothe laterally taken two-dimensional cephalometric x-ray. Thereafter, thereference hinge axis is constructed in the buccal view and perpendicularthereto using the x,y measurements made for the identifiable pointsrelative to the condyle axis in the x-ray.

[0138] As shown in FIG. 9, provision of hinge axis data (block 18)includes capturing the spatial coordinates (x, y, z) of at least threeidentifiable nonlinear points (e.g., incisor cusp tip, pits on left andright second molars, etc.) on the upper or lower dental arches of thepatient. For example, such spatial coordinates may be obtained using adigitizer from Immersion Corp. sold under the trade designation ofMicroscribe-3DX digitizer equipped with a stylus tip. The spatialcoordinates can be captured directly from the patient or from arepresentation of the patient that contains the relationship of theupper and lower dental arches, e.g., a bite impression. In addition, thecondyle axis on either side of the patient is located, e.g., using afacebow overlay technique such as described with reference to thefacebow apparatus of FIGS. 11A-11C, and the x, y, z position of thecondyle axis is determined. The x, y, and z coordinates of the condyleaxis along with the x, y, and z coordinates of the identifiable pointsof the dental arches are provided as the hinge axis data 18.

[0139] The facebow apparatus 100 as shown in FIGS. 11A-11C can be usedto accurately locate at least three positions of the dentition, e.g.,cusp tips of the upper arch, and the position of the condyle axisrelative to the dentition. Generally, a standard technique is toapproximate the condyle axis location as a standard distance from theear canal. Alternatively, a lateral cephalometric x-ray can provide therelationship between the ear canal and the condyle axis. Therefore, theear canal effectively locates the condyle axis of a patient. As such,the facebow apparatus uses the relationship between the ear canal andthe condyle axis to provide hinge axis data for use according to thepresent invention.

[0140] The facebow apparatus 100 includes a facebow portion 102, a bitefork portion 104, a nasion locator portion 106, which are all adjustablycoupled to a post 108. Facebow portion 102 includes an arcuate portion150 having a first section 153 and a second section 154 which are eachseparately movable about an axis 109 extending through the post 108 asrepresented by arrows 160 and 161 respectively. The facebow portion 102further includes ear canal insertion portions 152 at respective ends ofthe arcuate portion 150 for engagement with the ear canals of a patient.The facebow portion 102 is adjustable along the axis 109 as representedby double arrow 131. The adjusted position of the facebow portion 102can be measured by vertical measurement scale section 130 on the post108.

[0141] The bite fork portion 104 includes a bite impression portion 170which when used is filled with a wax compound or some other impressionmaterial 172 capable of retaining the impressions of the cusp tips ofthe upper dental arch. The bite fork portion 104 further includes aconnection member 174 which extends from the bite impression portion 170and is adjustably coupled through an opening 132 in post 108. As shownby double arrow 135, the bite fork is adjustable perpendicular to theaxis 109. Measurement for this adjusted position can be made permeasurement scale section 137 on the connection member 174. Further, thebite fork portion 104 is adjustable in an angular manner as shown bydouble arrow 139 about an axis 105 extending through the connectionmember 174 of the bite fork portion 104. Such an angular adjustedposition can be measured using the angular measurement scale section 134on post 108.

[0142] The nasion locator portion 106 includes a notch portion 116 whichis pressed against the bridge of a patient's nose and a locatorconnection portion 118 which is adjustable coupled to the post 108through a slot 120. The nasion locator portion 106 is adjustableperpendicular to the axis 108 as shown by double arrow 121. The adjustedposition of the nasion locator portion 106 is measured via themeasurement scale section 123 on the locator connection member 118.

[0143] In general, the position indications as provided by the variousmeasurement scale sections 130, 134, and 137 of the facebow apparatus100 determine the position and orientation of the bite fork portion 104with respect to the facebow portion 102. Since the components of theapparatus are all of known dimensions, the measurement data from themeasurement scale sections 130, 134, and 137 combined with the locationof the cusp tips on the bite plate completely represent the relativelocations of the condyle axis and the upper dental arch. The position ofthe nasion is also referenced to the condyle axis and the dental archesby the measurements of the measurement scale section 123 on the nasionlocator 106. It will be recognized that the various movable elements caninclude any suitable couplings that can be used for adjustment of theelements and/or locking of the movable elements in place.

[0144] The facebow apparatus 100 is used in the following manner. Thefacebow portion 102 via the ear canal insertion portions 152 is placedin the ear canals of a patient. The nasion locator 106 is position inthe slot 120 of the post 108 and the notch 116 is pressed against thebridge of the patient's nose. The nasion locator 106 is then locked intoplace in post 108. The bite fork portion 104 is loaded with impressionmaterial 172 and engaged into the post 108. The bite fork portion 104 ispositioned to locate the occlusal plane of the upper arch. The bite forkportion 104 is then pressed into the upper arch and the bite fork islocked into place in the post 108.

[0145] With the components locked into place, the measurement scalesections 130, 134, and 137 are read and noted. The facebow apparatus 100is then disassembled and the positions of at least three identifiablecusp tips are measured on the bite fork such as by a three dimensionaldigitizer. The cusp tip coordinate positions, the measurements notedfrom the measurement scale sections, and the known dimensions of thefacebow apparatus 100 provide the hinge axis data for attachment of areference hinge axis to the aligned dental arches. It should be apparentto one skilled in the art that electronic transducers may be used inplace of the measurement scales such that the data from such transducerscould be exported directly to a computer for use in creating the dentalmodel.

[0146] With the digital data representative of the upper and lowerdental arches provided to the model creation program 10 along with thegenerated hinge axis data as shown in FIG. 9 (e.g., facebow data), thehinge axis attachment routines 24 are performed as follows. The digitaldata representative of the upper and lower dental arches is manipulatedsuch that the upper and lower dental arch images represented by thedigital data are represented in a view corresponding to the x, y, and zcoordinates of the identifiable positions of the dental arches (e.g.,the at least three identifiable cusp tips). Thereafter, the referencehinge axis is constructed using the captured x, y, and z coordinatesdetermined for the condyle axis using a technique such as the facebowoverlay (e.g., the measurements of the measurement scale sections andthe known dimensions of the facebow components).

[0147] It will be readily apparent to one skilled in the art that theroutines as described with reference to FIGS. 1-9 may or may not requireuser input. For example, the alignment routines may be initiated by auser selecting for display an upper and lower dental image. Thereafter,the alignment of the upper and lower dental images relative to eachother may be performed automatically by the computing system usingroutines for accomplishing the functionality as described herein.Further, the attachment of the reference hinge axis may be performedautomatically upon selection of the applicable hinge axis data to beused for generating the articulation model. For example, with the hingeaxis data provided as shown in FIG. 8, the computing system willmanipulate the images of the dental arches to a buccal view and then usethe x, y coordinates to create the axis, i.e., a line, in the samecoordinate system as the manipulated images.

[0148] The centric occlusion bite registration algorithm 23 includingthe wobbling technique as presented summarily above with reference toFIG. 4, shall be described in further detail with reference to FIGS.10A-10C. The wobbling technique may be used to find the optimal centricocclusal relationship, i.e., determine proper occlusal contacts andoptimum cusp-fossa relationships between the teeth of the patient'supper and lower jaws (fossa/cusp interdigitation).

[0149] In general, the wobbling technique includes moving images of theupper and lower dental arches aligned along a plane towards each otheruntil a first contact point is detected, i.e., a pixel of the upperdental arch occupies the same coordinate position as a pixel of thelower dental arch. The images are then moved in one or more directionsrelative to one another in very small increments (preferably of pixelresolution) into a plurality of positions relative to the first contactpoint. Corresponding pixels of the upper and lower dental arches, i.e.,those lying along a similar coordinate axis, are compared to each otherat each of the positions to determine which position provides optimalinterdigitation between the upper and lower dental arches based on thedistance between the corresponding pixels at the plurality of positions.Thereafter, with the first contact point maintained, one of the upper orlower dental arch images may be rotated about an axis through the firstcontact point and perpendicular to the alignment plane to attain asecond point of contact between the upper and lower dental arch imagesin a region of the dental model symmetrically opposed to the region inwhich the first contact point resides.

[0150] In other words, the dental arch images are moved relative to eachother in very small increments, preferably of pixel resolution, to allowfor the determination of optimal occlusion of the lower and upper dentalarches, i.e. the dental arch images are wobbled relative to one anotherto determine optimal interdigitation. It will be apparent to one skilledin the art that such movement may be made in one or more directionsalong one or more coordinate axes or about one or more coordinate axesand that such movement is clearly not limited to the movement of theimages as described in the illustrative embodiment below.

[0151] FIGS. 10A-10C shows an illustrative example including use of thewobbling technique 23. First, back planes 77 of both an upper and lowerdental arch are created and the back planes 77 are aligned along analignment plane 75. For example, such alignment of the back planes maybe performed as described with reference to FIGS. 6A and 6B. Thereafter,the upper and lower dental arches are rotated as shown by the dentalmodel 71 on screen 73 such that the back planes are horizontal on thescreen 73 corresponding to alignment plane 75 as shown in FIG. 10B.

[0152] With the back planes 77 so aligned, phantom images of the upperand lower dental arch images are generated, i.e., images not displayedbut which preferably include only measured digital data representativeof dental arch images. A Z value for each pixel on the phantom image ofeach of the upper and lower phantom arch images is calculated, i.e.,Z_(upper), Z_(lower). In this particular illustrative embodiment, the Zvalue is a z coordinate value for each pixel as the back planes 77 arealigned along the z-coordinate plane.

[0153] The upper and lower phantom arch images are then moved closer toone another until a first contact point 72 is detected (FIG. 10C). Aftercontact is attained, a comparison of Z values for corresponding pixelsin the upper and lower phantom arch images is performed. The comparisonincludes calculating the distance between the corresponding pixels bytaking the difference between Z_(upper) and Z_(lower). The number ofcorresponding pixels in the upper and lower dental arch images having adistance therebetween below a certain threshold is then generated, i.e.,N1.

[0154] The upper dental arch image is then moved to the right and to theleft of the first contact point in pixel resolution, preferably onepixel. The number of corresponding pixels in the upper and lower dentalarch images having a distance therebetween that is below the thresholdis then generated for the positions of the upper dental image at theright and left of the first contact point, i.e., N2 and N3. N2 and N3are compared to N1 to determine if the position of the upper dental archcorresponding to N2 or N3 is a more optimal position than N1, i.e., thebest or optimal position being the position corresponding to the maximumnumber of corresponding pixels having a distance therebetween that fallbelow the threshold. The process of movement to the right or left of themore optimal position is repeated and calculations are continued untilthe position corresponding to the maximum number of corresponding pixelshaving a distance therebetween that is below the threshold is attained.

[0155] With the position of the upper dental arch image attainedcorresponding to the maximum number of corresponding pixels having adistance therebetween that is below the threshold, the dental modelincluding the upper and lower arch images is segmented symmetrically,i.e., in the middle, by plane 74 lying perpendicular to the alignmentplane 75 as shown in FIG. 10C. The symmetrically segmented dental model71 includes first half 79 and second half 80 with the first point ofcontact 72 lying in the first half 79. The upper dental arch image isthen rotated around an axis 81 extending through the first contact point72 and perpendicular to the back planes 77 or alignment plane 75, i.e.,parallel to the segmenting plane 74. The rotation is continued untilthere is a second contact point 70 attained in the second half 80 of thedental model. When the second contact point is attained, the optimalalignment position, i.e., occlusal relationship, of the upper and lowerdental arch images is achieved. Thereafter, upon attachment of thecondyle axis to the aligned upper and lower dental arch images, andoptionally attachment of the condyle geometry data, the dental model issaved, i.e., the file structure for the dental model is generated.

[0156]FIGS. 12A and 12B are illustrations of one embodiment of a graphicuser interface provided by the dental articulation user program 20 ofFIG. 1. If the condyle geometry is not already a part of the dentalmodel 210, the articulation interface may include input of condylegeometry data as shown in FIG. 12B, in addition to the hinge axis dataas represented in the model 210 by spheres 240. The hinge axis ispreferably a line segment connecting the center of the condyles. Inother words, the hinge axis represents the position of the condyles ofthe patient. FIG. 12B shows an articulator setup interface 250 with aview control interface 202 to be described in general below. The setupinterface 250 includes a left condyle input section 252 and a rightcondyle input section 254 which mimics the geometry used in mechanicalarticulators; such mechanical articulators typically have severaladjustments. Such common adjustments include the inclination of thefossa, i.e., the inclination angle, as shown by the right angle member241 on the model 210, and also the Bennett angle as represented by theplane member 242 on the model 210. Further, such adjustments may includevarious other input data, such as the width or distance between thecondyles as shown in the other input section 256. As shown by thegeneral nature of section 256, the other various adjustment factors maydepend on the type of articulator the user is trying to mimic.

[0157] Therefore, the condyle geometry can be approximated by suchsimple inputs into such input interface sections. These inputs can bebased on data such as population norms or patient specific data.Preferably, the condyle geometry is generated from clinical measurementsand is the condyle geometry data which has previously been describedwith reference to at least FIG. 1.

[0158] The screen display 200 of FIG. 12A shows a dental model 210including upper dental arch 212, lower dental arch 214, and condylehinge axis 216. The display further provides the view control interface202 and an articulation control interface 204 for allowing the user tomanipulate the dental model 210 as desired. The view control interface202 includes model icon 230 at the center of the interface with a firstset plane rotation element 234 thereabout, and a second set planerotation element 236 to the left of the first set plane rotation element234. The first and second set plane rotation elements allow the user torotate the model within the set planes. Further, the view controlinterface 202 includes a slide control 232 for allowing the user to movethe jaws relative to one another. For example, the interface may allowthe user to move at least one of the upper and lower dental archesrelative to the reference hinge axis or further, for example, theinterface may allow the user to hold the upper dental arch in a fixedposition with the lower arch being moved relative to the upper arch andthe reference hinge axis. A view control interface such as interface 202is described in Israeli Patent Application No. 120867 entitled “ComputerUser Interface For Orthodontic Use” filed May, 20, 1997 and assigned toCadent, Ltd. (Israel) which is hereby entirely incorporated by referenceherein.

[0159] Articulation control interface 204 includes protrude/retractslide control 218 for allowing the user to move the lower dental arch214 relative to the upper dental arch 212. For example, if the slidecontrol button 219 is positioned at the far end of the slide by theprotrude text as shown in FIG. 12A, the lower dental arch 214 is in amaximum protrude state relative to the upper dental arch 212. When theslide control button 219 is moved towards the retract portion of theslide control 218, the lower dental arch 214 is in a retracted staterelative to the upper dental arch 212.

[0160] Further, the articulation control interface 204 includes aleft/right slide control 220 for use in sliding the lower dental arch214 relative to the upper dental arch 212 in a direction along the hingeaxis 216. The actual lateral position of the lower arch relative to theupper arch is dependent on the position of slide button 221 relative tothe ends of the slide control 220.

[0161] The protruded or retracted position or the left or right slidingposition of the lower and upper dental arches may also be controlledusing dimensional changes provided by the user per inputs 228 and 226,respectively. For example, if the lower dental arch 214 is to be slid 3mm to the right relative to the upper dental arch 212, then 3 would beselected for input 226.

[0162] Further, the interface 204 includes centric relation button 222and centric occlusion button 224. Selection of the centric relationbutton 222 moves the dental arches 212, 214 relative to the hinge axis216 to a position representative of when the condyles of the patient arefully seated in the patient's fossas. The position of the model asstored upon creation is the centric occlusion position, i.e., theoriginating position. In other words, when the model is first brought upon the screen 200, the model is in centric occlusion. To show theposition of the model when in centric relation, the button 222 isselected. For example, the position of the elements of the model incentric occlusion is the position of the model after undergoingoptimization by the wobbling technique previously described. Theposition of the elements in centric relation is achieved by a threedimensional transformation of the model in centric occlusion using adelta measurement taken between the two positions such as with the useof a wax bite impression at centric occlusion relative to a wax biteimpression at centric relation.

[0163] In other words, generally, the interface provided by the userprogram 20 provides the ability for the user to view the dental model atany angle and/or magnification. The viewing algorithms are controlled bymouse activations and/or a keyboard, or any other mechanism forselecting or initiating computing actions or manipulation of images on ascreen as commonly used by one skilled in the art. Further, generally,the user is given the ability to manipulate the dental model forarticulation, either simple hinge or full articulation. For example, thejaw can be opened and closed by rotating the lower arch about the hingeaxis and/or the lower arch can be slid over the upper arch using theslide controls and collision detection, e.g., either simple contactdetection or a more complex collision detection technique similar to thewobbling technique previously described herein. Further, for example,initial hinge opening may be performed from centric relation whichinvolves rotation about the reference hinge axis of the model. Whenopening from positions other than centric relation, the motion of thecondyles may include various rotations and translations (e.g., 6 degreesof freedom). In other words, in full articulation, 6 degree of freedommotion of the mandible relative to the cranium can be simulated. Suchmotions may be limited by the constraints of the condyle geometry and/orcollision detection, also as previously described herein. The complexmotions of the lower arch image (a rigid body connected to the condyles)relative to the upper arch image (a rigid body connected to the fossas)can be determined, such as based on 3D sensor data.

[0164] It should be readily apparent that the items shown in the displayscreen 200 are only a few of the numerous interface elements or iconsthat may be used with the present dental model. For example, otherelements for bringing up the model, deleting a model, moving a model orany other elements typically used in graphic manipulation may be usedaccording to the present invention. Further, the present invention isclearly not limited to those elements and techniques described orillustrated herein, but only as described in the accompanying claims.For example, the dental model may be manipulated to provide occlusalmaps such as described in Israeli Patent Application No. 120892 entitled“Method For Obtaining a Dental Occlusion Map” filed May 22, 1997 andcurrently assigned to Cadent, Ltd. (Israel), hereby entirelyincorporated by reference.

[0165]FIG. 13 is a general block diagram illustration of an embodimentof the present invention in which additional graphics files 13 areattached to the dental model 11 according to the present invention. Theattached additional graphics files 13 can then be used under control ofthe dental articulation user program 20 and interface provided thereby.FIGS. 14 and 15 illustrate two techniques for attachment and use of suchgraphics files according to the present invention.

[0166] An image attachment method 280 is shown in FIG. 14. The use ofthe images attached via this method 280 is further illustrated in FIGS.16A and 16B. In the image attachment method 280, an image (e.g., any twoor three dimensional image) is digitized. For example, the images may befrom cephalometric x-rays, panoramic x-rays, patient photographs,intraoral photographs, and/or three dimensional scans of patients (e.g.,using Vivid 700 Digitizer available from Minolta Corp., Ramsey, N.J.).Three or more common points between the image and the dental model orarticulation model are identified. The three or more common pointsbetween the image and the dental model are then aligned to register theimage to the dental model. For example, one pair of common points may befirst aligned and then the image may be scaled and rotated relative tothe dental model such that all the identified common points arecoincident. The relationship between the image and the dental model isthen saved and provides a unified model of the patient which is usefulfor diagnosis. Thereafter, the dental model and the image may bedisplayed in any combination of registered images at any intensity. Forexample, one image can be faded out while the other fades in to viewcorresponding features. Even more simply, the image may be of adifferent intensity than the dental model.

[0167] One example of a digitized cephalometric x-ray image 320 havingtracings 322 thereon is shown in FIG. 16A on display screen 300. Thex-ray image 320 is attached or registered with dental model 310including upper and lower dental arches 312, 314, and condyle axis 316.As further shown, the dental model 310 with attached x-ray image 320 canthen be manipulated by view control interface 302 and articulationcontrol interface 304 as desired by the user and as previously describedabove. In FIG. 16B, the dental model 310 with the attached x-ray image320 is shown rotated from its previous position shown in FIG. 16A.

[0168] A method 290 of attaching a graphics file including motion datato the dental model is shown in the block diagram of FIG. 15. First, themotion of the mandible is recorded for later playback using the dentalmodel. To record the motion of the mandible, position sensors areattached to the patient's mandible and cranium. For example, suchsensors may be sensors available under the trade designation of Minibird6 degree of freedom sensors from Ascension Technology, Burlington, Vt.The position of the sensor on the cranium is measured with respect tothree points on the patient which correspond to identifiable points onthe dental model. i.e., the virtual articulator model. For example, suchpoints may be the incisor tip, left and right condyle, etc. The positionof the sensor on the mandible is also measured from three points on thepatient that correspond to three identifiable points on the dentalmodel. Such measurements may be made with a device like theMicroscribe-3DX digitizer.

[0169] Thereafter, a datum representing the sensor on the cranium iscreated for attachment to the dental model file for use in virtualarticulation. The cranium sensor datum is connected as a rigid body tothe upper dental arch and fossa data of the condyle geometry. Likewise,a datum representing the sensor on the mandible is created forattachment to the dental model file for use in virtual articulation. Themandible sensor datum is connected as a rigid body to the lower dentalarch and condyle data of the condyle geometry previously provided forthe patient.

[0170] Using a computer implemented system, or any other suitablerecording apparatus, the sensor output of the cranium and mandiblesensors are recorded at a known reference position. For example, theknown reference position may be a position with the arches in centricocclusion, in centric relation, etc. This creates an initial referencemeasurement position or a zero point from which all other measurementsof the sensor outputs are made and referenced. With the known referencemeasurement position established, the sensor positions are recorded as afunction of time as the patient undergoes desired mandibular excursions.

[0171] The data recorded is saved to a file for attachment to the dentalarticulation model. The recorded data representative of the motion ofthe mandible, i.e., the position sensor data, is used to manipulate theupper and lower dental arches of the dental model for articulation. Therecorded data is applied to the sensor location points on the upper andlower dental arches of the dental model using rigid body graphictransformations as the cranium sensor datum and the mandible sensordatum are connected as a rigid body to the upper arch and lower archrespectively. The recorded data can be used to play back the mandibularmotion to a user of the dental articulation model in real time, i.e.,substantially at the same time as the data is recorded, at a later time,in slow motion, reverse, etc. as would be known to one skilled in theart. Further, in accordance with the other aspects of the presentinvention, the dental model being played back with the mandibular motionmay be viewed from various angles, at various zoom levels, etc. as thedata is being played back.

[0172] It should be apparent to one skilled in the art, that if thecranium of the patient is fixed in placed during measurements used tosense the motion of the patient's mandible, or if the mandibular sensoris directly referenced to the cranium, then only the mandibular sensoris required to obtain the necessary measurements for recordingmandibular motion. For example, in such a circumstance, onlymeasurements using the mandibular sensor output and application of therecorded data to the location points on the lower arch are required toplay back the mandibular motion using the dental model.

[0173] All references and patents disclosed herein are incorporated byreference in their entirety, as if each were individually incorporated.Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scope ofthe invention, and it should be understood that this invention is not tobe unduly limited to the illustrative embodiments and processes setforth herein.

What is claimed is:
 1. A computer implemented method of creating adental model for use in dental articulation, the method comprising thesteps of: providing a first set of digital data corresponding to anupper arch image of at least a portion of an upper dental arch of apatient; providing a second set of digital data corresponding to a lowerarch image of at least a portion of a lower dental arch of the patient;providing hinge axis data representative of the spatial orientation ofat least one of the upper and lower dental arches relative to a hingeaxis of the patient; providing bite alignment data representative of thespatial relationship between the upper dental arch and the lower dentalarch of the patient; aligning the upper arch image and the lower archimage based on the bite alignment data; and creating a reference hingeaxis relative to the aligned upper and lower arch images based on thehinge axis data.
 2. The method according to claim 1, wherein the methodfurther includes displaying at least the upper and lower arch images andmanipulating the upper and lower arch images to move at least one of theupper and lower arch images relative to the reference hinge axis.
 3. Themethod according to claim 2, wherein the step of manipulating the upperand lower arch images includes retaining the upper arch image in a fixedposition and moving the lower arch image relative to the upper archimage.
 4. The method of claim 1, wherein the step of providing the hingeaxis data includes the steps of: providing a two-dimensional imageperpendicular to the hinge axis of the patient, the two-dimensionalimage representative of at least a portion of at least one of the upperand lower dental arches of the patient; locating the center of thecondyle of the patient on the two-dimensional image; locating two ormore identifiable locations of at least one of the upper and lowerdental arches on the two-dimensional image; and determining the spatialcoordinates of the two or more identifiable locations from the center ofthe condyle, wherein the reference hinge axis is created based on thespatial coordinates and digital data representative of locations of theupper and lower arch images corresponding to the two or moreidentifiable locations on the two-dimensional image.
 5. The methodaccording to claim 1, wherein the step of providing the hinge axis dataincludes the step of using a facebow apparatus to provide at least oneset of indicia representative of the spatial orientation of the upperdental arch of the patient relative to the hinge axis of the patient. 6.The method according to claim 5, wherein the step of using a facebowapparatus to provide at least one set of indicia representative of thespatial orientation of the upper dental arch of the patient relative tothe hinge axis of the patient includes the steps of: providing a facebowapparatus including a bite fork portion for use in obtaining animpression of at least a portion of the upper arch of the patient, anasion locator portion for pressing against the bridge of the patient'snose and a facebow portion for insertion into the patient's ear canals,each adjustably coupled to an adjustment post; determining coordinatesof three identifiable points of the upper dental arch using the bitefork portion; and obtaining measurements indicating the position of thebite fork portion relative to the facebow portion.
 7. The methodaccording to claim 5, wherein the step of providing hinge axis datafurther includes the steps of: providing coordinates of at least threeidentifiable positions on the upper dental arch of the patient;identifying at least three positions on the upper arch imagecorresponding to the identifiable positions; and determining the spatialcoordinates of the at least three positions on the upper arch image,wherein the reference hinge axis is created based on digital datarepresentative of the spatial coordinates and the at least one set ofindicia.
 8. The method according to claim 1, wherein the step ofproviding bite alignment data includes providing data representative ofat least one common geometrical feature of both the upper and lower archimages.
 9. The method according to claim 8, wherein the step ofproviding data representative of a common geometrical feature includesthe steps of: providing impressions of the upper and lower dental archesof the patient; providing a bite impression of the patient; aligning theupper and lower impressions with the bite impression; creating the atleast one common feature in the impressions of the upper and lowerdental arches; and digitizing the impressions of the upper and lowerdental arches resulting in the first and second set of digital datacorresponding to the upper and lower arch images and further resultingin bite alignment data representative of the at least one commonfeature, wherein the upper arch image and lower arch image are alignedbased on the bite alignment data representative of the at least onecommon feature.
 10. The method according to claim 9, wherein the atleast one common feature includes a line and a plane perpendicular tothe occlusal plane.
 11. The method according to claim 1, wherein thestep of providing bite alignment data includes the step of capturingspatial coordinates of at least three nonlinear positions of each of theupper and lower dental arches of the patient.
 12. The method accordingto claim 11, wherein the alignment step includes the steps of:identifying positions of the upper and lower arch images correspondingto each of the at least three nonlinear positions of the upper and lowerdental arches of the patient; and aligning the upper and lower archimages by bringing the identified positions of the upper and lower archimages into the same relationship as the spatial coordinates for the atleast three nonlinear positions of each of the upper and lower dentalarches of the patient.
 13. The method according to claim 11, wherein thestep of providing spatial coordinates includes capturing the spatialcoordinates for the at least three nonlinear positions of each of theupper and lower dental arches of the patient directly from the patient.14. The method according to claim 11, wherein the step of providingspatial coordinates includes capturing the spatial coordinates for theat least three nonlinear positions of each of the upper and lower dentalarches from a bite impression of the patient.
 15. The method accordingto claim 1, wherein the steps of aligning the upper arch image and thelower arch image and creating a reference hinge axis include the stepsof: manipulating the first and second set of digital data to move theupper and lower arch images relative to one another based on the bitealignment data until an aligned upper and lower arch image is attained;storing a third set of digital data representative of the aligned upperand lower arch images; determining a location of the reference hingeaxis relative to the aligned upper and lower arch images in the samecoordinate system as the aligned upper and lower arch images; andstoring a fourth set of digital data representative of the location,wherein the third set of digital data is linked to the fourth set ofdigital data.
 16. The method according to claim 15, wherein the step ofmanipulating the first and second set of digital data includes the stepsof: aligning the upper and lower arch images along a first plane; movingthe upper and lower arch images towards each other until a first contactpoint is detected; and moving at least one of the upper and lower archimages relative to the other in one or more directions and in relativelysmall increments to a plurality of positions for the determination ofoptimal occlusion of the lower and upper dental arches.
 17. The methodaccording to claim 16, wherein the moving step includes the steps of:computing the distance between corresponding pixels of the upper andlower arch images at one or more of the plurality of positions; anddetermining optimal occlusion based on the computed distances.
 18. Themethod according to claim 1, wherein the method further includesproviding data associated with condyle geometry of the patient.
 19. Themethod according to claim 18, wherein the method further includesdisplaying at least the upper and lower arch images and manipulating theupper and lower arch images to move the lower arch image relative to theupper arch image and the reference hinge axis, wherein the condylegeometry data provides limitations on the movement of at least the lowerarch.
 20. A computer implemented method of creating a dental model foruse in dental articulation, the method comprising the steps of:providing a first set of digital data corresponding to an upper archimage in a coordinate system of at least a portion of an upper dentalarch of a patient; providing a second set of digital data correspondingto a lower arch image in the coordinate system of at least a portion ofa lower dental arch of the patient; providing hinge axis datarepresentative of the spatial orientation of at least one of the upperand lower dental arches relative to a condylar axis of the patient; andcreating a reference hinge axis in the coordinate system relative to theupper and lower arch images based on the hinge axis data.
 21. The methodof claim 20, wherein the method further includes providing condylegeometry data representative of movement of the mandible of the patientto the cranium of the patient.
 22. The method according to claim 21,wherein the step of providing condyle geometry data includes the step ofproviding calculated condyle geometry data having a condylar axiscorresponding to the reference hinge axis, the method further includingthe step of creating data representative of the condyle geometry of thepatient in the coordinate system with the reference axis and the upperand lower arch images.
 23. The method according to claim 21, wherein themethod further includes displaying at least the upper and lower archimages and manipulating the upper and lower arch images to move at leastthe lower arch image relative to the upper arch image and the referencehinge axis, wherein the condyle geometry data provides limitations onthe movement of at least the lower arch image.
 24. A computerimplemented method of creating a dental model for use in dentalarticulation, the method comprising the steps of: providing a first setof digital data corresponding to an upper arch image of at least aportion of an upper dental arch of a patient; providing a second set ofdigital data corresponding to a lower arch image of at least a portionof a lower dental arch of the patient; providing bite alignment datarepresentative of the spatial relationship between the upper dental archand the lower dental arch of the patient; aligning the upper and lowerarch images relative to one another based on the bite alignment datauntil an aligned upper and lower arch image is attained; moving thealigned upper and lower arch images towards each other until a firstcontact point is detected; and moving at least one of the upper andlower arch images relative to the other in one or more directions to aplurality of positions for determining optimal occlusion position of thelower and upper dental arches.
 25. The method according to claim 24,wherein the moving at least one of the upper and lower arch imagesrelative to the other in one or more directions includes moving theimages in pixel resolution.
 26. The method according to claim 24,wherein the moving step includes the steps of: computing the distancebetween corresponding pixels of the upper and lower arch images at theplurality of positions; and determining the optimal occlusion positionbased on the computed distances.
 27. The method according to claim 26,wherein the determination step includes selecting the optimal occlusionposition as the position of the plurality of positions at which the mostcorresponding pixels having a distance therebetween that falls below aparticular distance threshold.
 28. The method according to claim 26,wherein the method further includes moving one of the upper and lowerarch images in another direction relative to one another when the upperand lower arch images are in the optimal occlusion position to attain asecond point of contact in a region of the aligned upper and lower archimages which lies symmetrically opposed to a region in which the firstcontact point is located.
 29. A computer implemented method of dentalarticulation, the method comprising the steps of: providing a dentalarticulation model, the model comprising: a first set of digital datacorresponding to an upper arch image of at least a portion of an upperdental arch of a patient, a second set of digital data corresponding toa lower arch image of at least a portion of a lower dental arch of thepatient, and a third set of digital data representative of the spatialorientation of the upper and lower arch images relative to a referencehinge axis, displaying at least the upper and lower arch images based atleast on the first and second sets of digital data; and manipulating oneor more of the first, second and third sets of digital data to move atleast one of the upper and lower arch images about the reference hingeaxis to simulate movement of the upper and lower dental arches of thepatient.
 30. The method according to claim 29, wherein the model furtherincludes a fourth set of digital data representative of the spatialorientation of condyle geometry of the patient relative to the referencehinge axis, and further wherein the manipulation of the digital dataincludes manipulation of the first, second, third, and fourth sets ofdigital data to move at least the lower arch image relative to the upperarch image and the reference hinge axis.
 31. The method according toclaim 32, wherein the manipulation of the digital data to move the lowerarch image relative to the upper arch image and the reference hinge axisis limited within the condyle geometry of the patient based on thefourth set of digital data.
 32. A computer implemented method of dentalarticulation, the method comprising the steps of: providing a dentalarticulation model, the model comprising: a first set of digital datacorresponding to an upper arch image of at least a portion of an upperdental arch of a patient, a second set of digital data corresponding toa lower arch image of at least a portion of a lower dental arch of thepatient, and a third set of digital data representative of the spatialorientation of the upper and lower arch images relative to a referencehinge axis; providing a fourth set of digital data representative of animage having at least three points corresponding to at least threeidentifiable points of the dental articulation model; and displaying atleast a portion of the dental articulation model registered with theimage based at least in part on the fourth set of digital data.
 33. Themethod of claim 32, wherein the fourth set of digital data isrepresentative of a two dimensional or three dimensional image.
 34. Themethod of claim 33, wherein the fourth set of digital data isrepresentative of an x-ray.
 35. A computer implemented method of dentalarticulation, the method comprising the steps of: providing a dentalarticulation model, the model comprising: a first set of digital datacorresponding to an upper arch image of at least a portion of an upperdental arch of a patient, a second set of digital data corresponding toa lower arch image of at least a portion of a lower dental arch of thepatient, and a third set of digital data representative of the spatialorientation of the upper and lower arch images relative to a referencehinge axis; providing a fourth set of digital data representative of aplurality of motion recordings of the patient's mandible; andmanipulating at least one of the first, second and third sets of digitaldata to move the lower arch image to simulate relative movement of thelower dental arch of the patient based at least on the fourth set ofdigital data.
 36. The method of claim 35, wherein the fourth set ofdigital data includes at least three points of the mandiblecorresponding to at least three identifiable points on the lower archimage of the dental model, the fourth set of digital data furtherincluding data representing at least a known reference position of thelower dental arch of the patient and one or more positions of the lowerdental arch relative to the known reference position.
 37. A computerreadable medium tangibly embodying a program executable for creating adental model for use in dental articulation, the computer readablemedium comprising: means for recognizing a first set of digital datacorresponding to an upper arch image of at least a portion of an upperdental arch of a patient, a second set of digital data corresponding toa lower arch image of at least a portion of a lower dental arch of thepatient, hinge axis data representative of the spatial orientation of atleast one of the upper and lower dental arches relative to a hinge axisof the patient, and bite alignment data representative of the spatialrelationship between the upper dental arch and the lower dental arch ofthe patient; first program means for creating a third set of digitaldata representative of an aligned upper arch image and lower arch imagebased on the bite alignment data and the first and second sets ofdigital data; and second program means for creating a fourth set ofdigital data representative of the spatial orientation of a referencehinge axis relative to the aligned upper and lower arch images based atleast in part on the hinge axis data.
 38. The computer readable mediumof claim 37, wherein the recognition means includes means forrecognition of condyle geometry data, and wherein the medium furtherincludes means for creating a fifth set of digital data representativeof the spatial orientation of condyle geometry of the patient to thereference hinge axis.
 39. A computer readable medium tangibly embodyinga program executable for performing dental articulation, the computerreadable medium comprising: a dental articulation model comprising atleast a first set of digital data corresponding to an upper arch imageof at least a portion of an upper dental arch of a patient aligned witha lower arch image of at least a portion of a lower dental arch of thepatient, and a second set of digital data representative of the spatialorientation of a reference hinge axis relative to the aligned upper andlower arch images; means for displaying at least the upper and lowerarch images; and means for manipulating the first set of digital data tomove at least one of the upper and lower arch images about the referencehinge axis to simulate movement of the upper and lower dental arches ofthe patient.
 40. The computer readable medium according to claim 39,wherein the dental model further includes a third set of digital datarepresentative of the spatial orientation of condyle geometry of apatient relative to the reference hinge axis, and further wherein themanipulation means includes means for manipulating the first set ofdigital data to move at least the lower arch image relative to the upperarch image and the reference hinge axis.
 41. A facebow apparatus,comprising: a bite fork portion for use in obtaining an impression of atleast a portion of an upper dental arch of a patient; a nasion locatorportion for pressing against the bridge of the patient's nose; a facebowportion for insertion into the patient's ear canals, wherein each of thebite fork portion, the nasion locator, and the facebow portion areadjustably coupled to an adjustment post; and measurement scale meansfor providing a set of indicia representative of the spatial orientationof the upper dental arch of the patient relative to a condyle axis ofthe patient.
 42. A dental model created by performing the steps recitedin claim
 1. 43. A series of display images resulting from theperformance of the steps recited in claim 29 representative of themovement of the at least one of the upper and lower arch images.
 44. Acomputer implemented method of creating a dental model for use in dentalarticulation, the method comprising: providing a first set of digitaldata corresponding to an upper arch image of at least a portion of anupper dental arch of a patient; providing a second set of digital datacorresponding to a lower arch image of at least a portion of a lowerdental arch of the patient; providing hinge axis data representative ofthe spatial orientation of at least one of the upper and lower dentalarches relative to a hinge axis of the patient; providing bite alignmentdata representative of the spatial relationship between the upper dentalarch and the lower dental arch of the patient; aligning the upper archimage and the lower arch image based on the bite alignment data andcreating a reference hinge axis relative to the aligned upper and lowerarch images based on the hinge axis data, wherein aligning the upperarch image and the lower arch image and creating the reference hingeaxis comprises: manipulating the first and second set of digital data tomove the upper and lower arch images relative to one another based onthe bite alignment data until an aligned upper and lower arch image isattained; storing a third set of digital data representative of thealigned upper and lower arch images; determining a location of thereference hinge axis relative to the aligned upper and lower arch imagesin the same coordinate system as the aligned upper and lower archimages; and storing a fourth set of digital data representative of thelocation of the reference hinge axis, wherein the third set of digitaldata is linked to the fourth set of digital data; and determining anoptimal occlusion for the aligned lower and upper dental arches, whereindetermining the optimal occlusion comprises: moving the upper and lowerarch images towards each other until a first contact point is detected,and moving at least one of the upper and lower arch images relative tothe other in one or more directions and in relatively small incrementsto a plurality of positions.
 45. The method according to claim 44,wherein determining optimal occlusion for the aligned lower and upperdental arches further comprises: computing the distance betweencorresponding pixels of the upper and lower arch images at one or moreof the plurality of positions; and determining optimal occlusion basedon the computed distances.
 46. The method according to claim 44, whereinthe method further comprises displaying at least the upper and lowerarch images and manipulating the upper and lower arch images to move atleast one of the upper and lower arch images relative to the referencehinge axis.
 47. The method according to claim 46, wherein manipulatingthe upper and lower arch images comprises retaining the upper arch imagein a fixed position and moving the lower arch image relative to theupper arch image.
 48. The method of claim 44, wherein providing thehinge axis data comprises: providing a two-dimensional imageperpendicular to the hinge axis of the patient, the two-dimensionalimage representative of at least a portion of at least one of the upperand lower dental arches of the patient; locating the center of thecondyle of the patient on the two-dimensional image; locating two ormore identifiable locations of at least one of the upper and lowerdental arches on the two-dimensional image; and determining the spatialcoordinates of the two or more identifiable locations from the center ofthe condyle, wherein the reference hinge axis is created based on thespatial coordinates and digital data representative of locations of theupper and lower arch images corresponding to the two or moreidentifiable locations on the two-dimensional image.
 49. The methodaccording to claim 44, wherein providing the hinge axis data comprisesusing a facebow apparatus to provide at least one set of indiciarepresentative of the spatial orientation of the upper dental arch ofthe patient relative to the hinge axis of the patient.
 50. The methodaccording to claim 44, wherein providing hinge axis data furthercomprises: providing coordinates of at least three identifiablepositions on the upper dental arch of the patient; identifying at leastthree positions on the upper arch image corresponding to theidentifiable positions; and determining the spatial coordinates of theat least three positions on the upper arch image, wherein the referencehinge axis is created based on digital data representative of thespatial coordinates and the at least one set of indicia.
 51. The methodaccording to claim 44, wherein providing bite alignment data comprisesproviding data representative of at least one common geometrical featureof both the upper and lower arch images.
 52. The method according toclaim 51, wherein providing data representative of a common geometricalfeature comprises: providing impressions of the upper and lower dentalarches of the patient; providing a bite impression of the patient;aligning the upper and lower impressions with the bite impression;creating the at least one common feature in the impressions of the upperand lower dental arches; and digitizing the impressions of the upper andlower dental arches resulting in the first and second set of digitaldata corresponding to the upper and lower arch images and furtherresulting in bite alignment data representative of the at least onecommon feature, wherein the upper arch image and lower arch image arealigned based on the bite alignment data representative of the at leastone common feature.
 53. The method according to claim 52, wherein the atleast one common feature comprises a line and a plane perpendicular tothe occlusal plane.
 54. The method according to claim 44, whereinproviding bite alignment data comprises capturing spatial coordinates ofat least three nonlinear positions of each of the upper and lower dentalarches of the patient.
 55. The method according to claim 54, whereinaligning the upper arch image and the lower arch image comprises:identifying positions of the upper and lower arch images correspondingto each of the at least three nonlinear positions of the upper and lowerdental arches of the patient; and aligning the upper and lower archimages by bringing the identified positions of the upper and lower archimages into the same relationship as the spatial coordinates for the atleast three nonlinear positions of each of the upper and lower dentalarches of the patient.
 56. The method according to claim 54, whereinproviding spatial coordinates comprises capturing the spatialcoordinates for the at least three nonlinear positions of each of theupper and lower dental arches of the patient directly from the patient.57. The method according to claim 54, wherein providing spatialcoordinates comprises capturing the spatial coordinates for the at leastthree nonlinear positions of each of the upper and lower dental archesfrom a bite impression of the patient.
 58. The method according to claim44, wherein the method further comprises providing data associated withcondyle geometry of the patient.
 59. The method according to claim 58,wherein the method further comprises displaying at least the upper andlower arch images and manipulating the upper and lower arch images tomove the lower arch image relative to the upper arch image and thereference hinge axis, wherein the condyle geometry data provideslimitations on the movement of at least the lower arch.
 60. A computerimplemented method of creating a dental model for use in dentalarticulation, the method comprising: providing a first set of digitaldata corresponding to an upper arch image of at least a portion of anupper dental arch of a patient; providing a second set of digital datacorresponding to a lower arch image of at least a portion of a lowerdental arch of the patient; providing bite alignment data representativeof the spatial relationship between the upper dental arch and the lowerdental arch of the patient; aligning the upper and lower arch imagesrelative to one another based on the bite alignment data until analigned upper and lower arch image is attained; moving the aligned upperand lower arch images towards each other until a first contact point isdetected; and moving at least one of the upper and lower arch imagesrelative to the other in one or more directions to a plurality ofpositions for determining an occlusion position of the lower and upperdental arches.
 61. The method according to claim 60, wherein moving atleast one of the upper and lower arch images relative to the other inone or more directions comprises moving the images in pixel resolution.62. The method according to claim 60, wherein moving at least one of theupper and lower arch images relative to the other in one or moredirections comprises: computing the distance between correspondingpixels of the upper and lower arch images at the plurality of positions;and determining the occlusion position based on the computed distances.63. The method according to claim 62, wherein determining the occlusionposition comprises selecting an optimal occlusion position as theposition of the plurality of positions at which the most correspondingpixels having a distance therebetween that falls below a particulardistance threshold.
 64. The method according to claim 62, wherein themethod further comprises moving one of the upper and lower arch imagesin another direction relative to one another when the upper and lowerarch images are in the optimal occlusion position to attain a secondpoint of contact in a region of the aligned upper and lower arch imageswhich lies symmetrically opposed to a region in which the first contactpoint is located.
 65. A computer readable medium tangibly embodying aprogram executable on a computer apparatus for creating a dental modelfor use in dental articulation, wherein the computer readable mediumwhen executing is operable to: recognize a first set of digital datacorresponding to an upper arch image of at least a portion of an upperdental arch of a patient; recognize a second set of digital datacorresponding to a lower arch image of at least a portion of a lowerdental arch of the patient; recognize bite alignment data representativeof the spatial relationship between the upper dental arch and the lowerdental arch of the patient; align the upper and lower arch imagesrelative to one another based on the bite alignment data until analigned upper and lower arch image is attained; move the aligned upperand lower arch images towards each other until a first contact point isdetected; and move at least one of the upper and lower arch imagesrelative to the other in one or more directions to a plurality ofpositions for determining an occlusion position of the lower and upperdental arches.
 66. The computer readable medium according to claim 65,wherein the computer readable medium is further operable to move theimages in pixel resolution.
 67. The computer readable medium accordingto claim 65, wherein the computer readable medium is further operableto: compute the distance between corresponding pixels of the upper andlower arch images at the plurality of positions; and determine theocclusion position based on the computed distances.
 68. The computerreadable medium according to claim 67, wherein the computer readablemedium is further operable to select an optimal occlusion position asthe position of the plurality of positions at which the mostcorresponding pixels having a distance therebetween that falls below aparticular distance threshold.
 69. The computer readable mediumaccording to claim 67, wherein the computer readable medium is furtheroperable to move one of the upper and lower arch images in anotherdirection relative to one another when the upper and lower arch imagesare in the occlusion position to attain a second point of contact in aregion of the aligned upper and lower arch images which liessymmetrically opposed to a region in which the first contact point islocated.